Typical materials which are used as substrates for holographic emulsions include glass and polyester film material. Glass, an amorphous material, has optical properties which make it an excellent substrate for holography. Glass, however, is costly, fragile, and cannot be used in processes which require a flexible substrate, such as embossed holography.
MYLAR.TM., Kapton.RTM. and other organic film materials are used as flexible substrates for holographic emulsions but they have a birefringent property that changes the polarization of laser light used in making holograms. Such birefringence causes unwanted "noise" in the final hologram.